1. Stir together first 3 ingredients in a 5 1/2-qt. slow cooker.
2. Sprinkle roast evenly with flour, salt, and pepper. Brown roast on all sides in hot oil in a large Dutch oven over medium-high heat. Transfer roast to slow cooker.
3. Cover and cook on LOW 8 hours.
4. Remove roast from slow cooker; slice to serve. Skim fat from gravy in slow cooker, if desired. Whisk gravy; serve over roast.